1. Field of the Invention
This invention relates to the field of disk drive suspension assemblies. More particularly, this invention relates to the field of a method and structure for localizing solder ball strain on the gimbal of a hard disk drive suspension assembly.
2. Description of Related Art
A hard disk drive (HDD) unit generally uses a spinning storage medium (e.g., a disk or platter) to store data. A read-write head is positioned in close proximity to the spinning storage medium by a suspension assembly. A suspension assembly commonly includes a base plate, a load beam, and a flexure trace gimbal to which a slider is mounted. The slider supports the read-write head transducer element. The load beam is generally composed of an actuator mounting section, a spring region, and a rigid region. The spring region gives the suspension a spring force or preload counteracting the aerodynamic lift force created by the spinning medium during reading or writing. A gimbal is mounted at the distal end of the load beam and supports the slider allowing the head to have pitch and roll movement in order to follow the irregularities of the disk surface. The suspension assembly is moved by a voice coil motor, sometimes simply called an actuator motor.
A typical suspension assembly includes a flex trace formed or applied to the top of the load beam. The flex trace typically comprises an insulating layer such as polyimide, with electrically conducting traces such as copper traces formed on the polyimide. The electrical traces carry the data read signals and the data write signals. The flex traces terminate at bonding pads at the distal end of the flex trace. The bonding pads must be connected somehow to the electrical connection points on the slider. Known methods of electrically connecting the bonding pads to the slider include gold ball bonding and solder ball bonding. Solder ball bonding is accomplished by positioning a solder ball at the head slider and trace bonding pads, and applying heat at or near the solder ball. The heat melts the solder ball. The solder wets to the head slider and to the trace bonding pads.
One problem with solder ball bonding is that expansion and contraction due to heating and cooling during and after the solder ball bonding process and the resulting strains can cause distortion in the head suspension components at or near the bonding region, which can affect head suspension characteristics such as pitch static attitude (PSA).
One attempt to mechanically and thermally isolate the solder bonding area in order to minimize this distortion is disclosed in U.S. Pat. No. 6,965,499 issued to Zhang et al. Zhang et al. disclose a dielectric cross member on which the bonding pads are located, with the dielectric cross member being supported at its central portion by a longitudinally extending beam that is connected on one side to the gimbal tongue.
A second structure for a hard disk drive suspension gimbal with solder ball bonding is shown in U.S. Patent Publication No. 2006/0262456 A1 by Wang et al, which discloses a structure featuring a gimbal tongue near the distal end of a suspension. The solder ball bonding pads are located near where the gimbal tongue begins. Angled slots at the juncture of a gimbal cross bar and the gimbal tongue purportedly relieve stress on the gimbal. Cutouts in the vicinity of the bonding pads allow the magnetic read/write head in the slider to be electrically bonded to one or more bonding pads present on the other side of the gimbal tongue.